Brilliant, self replicating printers.
There's a piece somewhere on t'internet about how we could create self-powered swarms of co-operating robots equipped with prospecting, mining, refining and printing capabilities. Send a load of them off to Mars or somewhere a decade or two before we want to send colonists and they'll have created a whole habitat ready for the colonists to move into.
Or more practically, imagine setting a load of them to explore, extract and recycle useful materials from our massive waste landfill sites.
